Downdraft burner



May 51 953 J. E. Mccu 7,376

DOWNDRAFT BURNER Filed June 19, 1951 ,ZEQQZ a %y W ATTORNEYS.

Patented May 5, 1953 UNITED STATES PATENT OFFICE DOWNDRAFT BURNER John E. McCutchen, Wichita, Kans., assignor to The Coleman Company, Inc., Wichita, Kans., a corporation of Kansas I Application June 19, 1951, Serial No. 232,253

Claims.

This invention relates to a burner assembly adapted to burn downwardly in a down draft tube. This burner assembly has particular utility for use in immersion heaters having a pipe structure consisting of a generally vertical burner tube and a, generally vertical stack tube arranged in side-by-side relation and communicating with each other at their lower ends. This burner assembly can also be used in other applications.

Immersion heaters of the type with which this burner assembly has particular utility are widely used by the military services for outdoor heating of cans of water. Heaters of this type also have utility as stock tank heaters, and similar applications. These heaters are characterized by a distinctive pipe structure whose purpose is to allow the burner to be positioned below the water or other liquid in which the pipe structure is submerged, and to facilitate the transfer of heat from the burner flame and combustion gases to the liquid surrounding the pipe structure. The pipe structure which has been found satisfactory for this purpose is characterized by having a generally vertical burner tube and a generally vertical stack tube arranged in side-byside relation and communicating with each other at their lower ends.

In operation the immersion heater pipe structure is mounted in a generally vertical position within a container filled with the liquid to be heated so that the open upper ends of the burner tube and stack tube project above the surface of the liquid. Within the burner tube generally at about midway there is positioned a burner designed to burn downwardly in the burner tube. A stack is attached to the top of the stack tube for exhausting the combustion gases. During normal operation, the combustion air enters through the top of the burner tube and mixes with the fuel at the burner level to produce a downwardly projecting flame. This flame and the resulting combustion gases are sucked downwardly to the bottom of the burner tubeand through the communicating passage into the stack tube, and then move upwardly through the stack tube and are exhausted through the stack.

One problem which has arisen in connection with immersion heaters of this type is that of establishing a down draft in the burner tube and an up draft in the stack tube. When the burner is first ignited the initial tendency of the flame is to burn upwardly in the burner tube, and to draw air downwardly through the stack tube. Since this is exactly opposite to the desired direction of the draft in both tubes, it is necessary to 2 by the use of a torch is an awkward and inconvenient procedure, and therefore it is desired to provide means for automatically establishing the correct draft.

Heretofore the burners employed in immersion heaters have consisted of wick elements contained within a housing and exposed at the bottom thereof to provide the source of the downwardly orientated flame. A liquid fuel is generally fed onto these wick elements by a gravity feed and vaporized on the exposed portions thereof by the heat of the flame. Thus, the flame produced by such burners does not project downwardly with great force, and in fact would burn upwardly if it were not for the established down draft. Furthermore, it has been found that it is very difficult to supply sufficient air to these burners for efficient combustion at high rates of fuel combustion due to the peculiarities of the immersion heater pipe structures in which the combustion air must be sucked into the top of the burner tube.

It is therefore an object of this invention to provide a burner assembly particularly adapted for use in immersion heater pipe structures; which will substantially overcome the above problems. More specifically, it is an object of this invention to provide a burner assembly for use in immersion heaters which will produce jets of flame blasting downwardly with sufficient force to automatically establish the desired draft, and to materially increase the volume of combustion air sucked into the top of the burner tube. It is a further object of this invention to provide means associated with the burner to facilitate the transfer of heat from the combustion gases through the pipe structure walls to the surrounding liquid, and more particularly to accomplish this by imparting a rotary or spiral motion to the combustion gases. It is also an object of this invention to modify the walls of the pipe structure through which the combustion gases pass to maintain the spiral motion of the gases and to facilitate the transfer of heat from the spiraling gases. Further objects and advantages will appear as the specification proceeds.

This invention is shown in a preferred embodiment in the accompanying drawing, in which Figure 1 shows the complete burner assembly mounted in the down draft tube of an immersion heater pipe structure adapted to facilitate heat transfer; Fig. 2, an enlarged cross-sectional view of the burner of Fig. 1 showing the interior structure including the baffle plates; and Fig. 3, a top view of the burner of Fig. 2 partially broken away to show the staggered openings in the interior bafiie plates.

In the illustration given, the burner assembly comprises an elongated casing Hl having closed ends and providing interiorly a vaporization transfer from the exterior of the casing to the interior chamber I I.

A fuel supply pipe I2 terminates within chamber II for supplying liquid fuel I3 to the lower portion of chamber II for vaporization. In the illustration given, fuel supply pipe I2 enters through the top end of easing III and extends centrally to a short distance from the bottom end of easing I0.

If desired, supply pipe I2 can be segmented together with casing ID to facilitate assembly and .disassembly .of the burner. In theillustration given, "the upper portion Ida of casing It is received within the flared upper end of casing portion IIJb. Any suitable means can be provided for securing the overlapping casing portions :IOa and I912 together, such as spot welding. .A pipe sleeve I2a is secured in the upper end of easing III being interiorly threaded at its top and bottom ends. An upwardly extending pipe 120 is threadedly connected to the upper end of sleeve I211, and has .a downwardly extending reduced pipe I'2d which extends to a point near the bottom enclof casing I0. Communicating with the upper portion of vaporization chamber H are a plurality of vapor outlet pipes I4. Outlet pipes M extend downwardly along the outer surface of the casing at a spaced distance therefrom and terminate in open ends Ida above the lower end of casing It]. The open ends Ma of outlet pipes III are received within open ended flame tubes IE to control the supply of combustion air to the base of the flame jets. In the illustration given, name tubes i extend downwardly well below outlet pipe ends I 4a and have their lower pOltiOIlS provided with a plurality of spaced apertures I 5 for the supplying of additional air .to' the body of the flame Jets.

In order to control the pressure of the vaporized fuel within the upper portion of chamber I I, and particularly to eliminate fluctuation and surging causedby the rapid evaporization of fuel, it has been found desirable to interpose between the lower and upper portion of chamber I I a plurality of battle members having staggered openings. Any suitable baffle structure can be employed'for this purpose. In the illustration given, a plurality of closely spaced plates I? are secured to a supporting .stem I8 which has its upper end threaded into the lower end of sleeve I2a. Openings are provided in staggered relation through plates I'I. Openings I'Ia being formed around the periphery of plates I! by folding portions I "I0 downwardly, and openings IIb are provided centrally by folding portions I'Id downwardly. In the illustration given, downward portions I10 and I Id assist in supporting the plates in stacked relation. At least the lowermost of the plates, and if desired all of the plates, can be ri idly fastened to stem I8 so that they can easily be inserted in and removed from chamber I I.

In the illustration given and preferably, the lowerportion of chamber II is filled with wicking material I 8 to a level above the end of supply ipe: I2d but below the lowermost of the bafiie plates I'I. Wicking material I8 can consist of any material which is capable of resisting the heat to which the material is subjected and of assisting in vaporizing the fuel by capillary action- Below the lower end of easing II] and in the path of the flame jets it is desirable to provide a flame spreader I9 to somewhat diminish the forward velocity of the'fiame and to spread the v flame into many small streams. It is also desired to impart a whirling or spiraling motion to the combustion gases to facilitate combustion and heat transfer. In the illustration given, flame spreader I9 consists of a multi-bladed fan having inclined blades or vanes I9c mounted on the lower end of a metal coupling 20 having its upper end attached to the lower end of easing Ill. The employment of a metal coupling 20 to attach flame spreader I9 to the lower end of easing I0 allows heat to be conducted from flame spreader 'IE to the bottom portion of easing .III to assist the vaporization of the fuel. A flame spreader or the type desired is shown in greater detail in my co-pending application U. vS. Serial No. 192,271, filed October 26, 195.0, for Burner Assembly.

As shown more clearly in Fig. 1, the burner assembly of Fig. 2 is mounted so as to burn'downwardly in a down .drafttube. When mounted in this manner in a down draft tube, it has been found desirable to mount an air bafile 2i having a Venturi-type opening 2|.a around casing I0 in the region below the lower openings of flame tubes I5 to increase the velocity of the air entering the down draft tube and passing the flame jets. It has also been found desirable to provide a shield 22 around or above the upper portion of easing Iii to prevent direct impingement of the incoming cold air on the .top of easing I9 and the upper ends of outlet pipes I4. The purpose of shield 22 is to prevent the fuel vapor from condensing in the upper portion of chamber II or in outlet pipes I4 due to the cooling effect of the incoming air. In the illustration given, shield 22 is in the form of an inverted metal cup having its sides and bottom spaced from the surface of easing I0. It will be understood, however, that other shielding or insulating members can be substituted for cup 22, such as an asbestos disk, etc.

Figure 1 illustrates the employment of the burner of Fig. 2 in an immersion heater pipe structure composed of a generally vertical burner or intake tube 23 arranged in side-by-side relation with a generally vertical stack or exhaust tube 24 communicating with each other at their lower ends through a laterally extending tube25. In the illustration given, laterally extending tube 25 is doughnut-shaped and is provided therearound with a plurality of indentations 25. Preferably, indentations 26 have smoothly curved-surfaces protruding into the interior of cup 2 6. It has been found that it is desirable to have indentations 26 in the shape of hemispheres. This shape promotes heat transfer by allowing portions of the liquid surrounding the pipe structure to extend into the path of the combustion gases without unduly retarding the movement of the gases or stopping their spiraling motion produced by spreader l9. Preferably, stack tube 24 is also provided with spiral rows of indentations 2.6 having the shape of hemispheres.

It will be understood that doughnut tube 25 is provided at its rear with a partition member between down draft tube 23 and up draft tube 24 so that the combustion gases must flow around the forward portion .of tub 25 t pass from t 23 to tube 24. Exhaust tube 24 is also provided with a stack2l, whichcan be or any desired In the operation of the immersion heater pipe I structure employing the burner assembly as shown in Fig. 1, the pipe structure is immersed in the liquid to be heated with the burner mounted in the burner tube and the stack attached to the stack tube. A volatile liquid fuel is then supplied to the burner through pipe I2. Any suitable liquid fuel can be employed such as gasoline, kerosene, or alcohols. If desired, means can be provided for metering the supply of fuel through pipe [2.

Liquid fuel l3 collects in a pool in the bottom of vaporization chamber H. A torch is then applied to the bottom of casing H to vaporize fuel 13 so as to produce a supply of fuel vapor at elevated pressure within the upper portion of chamber H. The generation of the fuel vapor by the application of the torch causes the fuel vapor to pass outwardly through outlet pipes M. The vaporized fuel ignites at open ends Ma of the fuel outlet pipes to form downwardly projecting flame jets which heat the lower portion of easing Ill, and thereby permit the removal of the torch after a short starting period. It has been found that the flame jets blast downwardly with sufiicient force through spreader 19 to establish the desired down draft in tube 23 and up draft in tube 2 5. Furthermore, the flame jets increase the suction within tube 23 and thereby increase the volume of the air entering at the top of the tube. Thus, the burner can be operated at high rates of fuel consumption with substantially complete combustion of fuel.

Baiiie plates I! have been found very effective in preventing surging or fluctuation of the pressure of the vaporized fuel within the upper portion of chamber I I.

Spreader l9 produces a whirling motion of the combustion gases which assists in transferring of heat to the liquid surrounding the pipe structure, and cooperates with the rounded indentations 26 in effecting the transfer of heat, as explained above.

While in the foregoing specification there has been set forth particular embodiments of this invention for purpose of illustration, it will be understood that many of the details of the structures shown can be varied widely without departing from the spirit of the invention.

I claim:

1. A burner for liquid fuels adapted to burn downwardly in a down draft tube, comprising an elongated casing having closed ends and providing interiorly a vaporization chamber, wicking material filling the bottom end portion of said chamber, a fuel supply pipe terminating within said Wicking material to supply liquid fuel to the lower portion of said chamber for vaporization, a plurality of bafile plates extending across said vaporization chamber above said wicking material, said bafiie plates having staggered openings therethrough to cause the vaporized fuel to pass upwardly in circuitous paths, a plurality of outlet pipes communicating with the upper portion of said chamber above said bafiie plates and extending downwardly along the outer surface of said casing at a spaced distance therefrom, said outlet pipes terminating in open ends above the lower end of said casing so as to direct flame jets downwardly into the region around the bottom of said casing to heat the same and thereby vaporize said liquid fuel, and open ended flame tubes receiving the open end of said outlet pipes and extending therebelow to control the flow of air around the base of said flame jets.

[2. The burner of claim 1 having a spreader with closely spaced inclined blades positioned below the bottom end of said casing and in the path of said flame jets, and a metal coupling connecting the spreader with the lower end portion of said casing to transmit heat from said spreader to said casing and thereby increase the rate of fuel vaporization.

3. The burner of claim i having an air bafiie associated therewith providing a Venturi-type opening around said casing in the region of the lower ends of said flame tubes to increase the velocity of air through said region.

4. The burner of claim 1 having a shield member positioned above the upper end of said vaporizing chamber and in the path of the incoming air to prevent impingement of said air on the upper end portion of said casing.

5. A burner for liquid fuels adapted to burn downwardly in a downdraft tube, comprising an elongated casing having closed ends and providing interiorly a vaporizing chamber, a fuel pipe terminating within said chamber for supplying liquid fuel to thelower portion thereof for vaporization, a plurality of outlet pipes communicating with the upper portion of said chamber and extending downwardly in spaced relation along the outer surface of said casing, each of said outlet pipes terminating in an open end above the lower end of said casing arranged todirect a flame jet downwardly into the region about the bottom of said casing, and a separate open-ended tube receiving the open end of each of said outlet pipes and extending therebelow to control the flow of air to the base of said flame jet, and interposed in said vaporization chamber between the lower portion thereof and the point of communication of said outlet pipes, a plurality of baffle plates extending across said chamber having staggered openings therethrough to promote uniform pressure in the upper portion of said vaporization chamber, the lower portion of said chamher being packed with wicking material to a level above the lower end of said fuel pipe.

JOHN E. MCCUTCHEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 483,730 Ball Oct. 4, 1892 949,073 Herriff Feb. 15, 1910 1,261,799 Elliott Apr. 9, 1918 1,288,171 Pinal Dec. 17, 1918 1,524,465 Wray Jan. 27, 1925 1,690,659 Wykes Nov. 6, 1928 2,247,239 Keating June 24:, 1941 2,443,707 Korsgren June 22, 1948 FOREIGN PATENTS Number Country Date 12,438 Great Britain of 1897 255,493 Italy Oct. 25, 1927 392,747 Great Britain May 25, 1933 

